The present invention encompasses sensing means for monitoring the cardio-pulmonary functions of a patient, especially new born babies in an intensive care unit. According to the present invention up to four functions or parameters; PO.sub.2, PCO.sub.2, the respiration rate and encardiography are measured in both a simultaneous and transcutaneous way. Among the above four functions the first two are relatively new while the latter items have been practiced for a long time.
As is generally known, the respiration rate and encardiography are measured such that two electrodes 2, 2' are applied to predetermined portions on the skin of the human subject 1 and fluctuations in the potential between the electrodes are taken as a measure of encardiography, while fluctuations in the impedance between these electrodes are used to measure the respiration rate. Referring to FIG. 1, signals related to the two mentioned functions are led to a resistor R, and signals related to the heartbeat (of low frequency) are taken out by means of a low-pass filter 3 connected across the resistor R, while an alternate source of 50 kHz supplied for measurement is taken out by means of a tuning circuit 4 and detected in order to measure the respiration rate. Accordingly, two electrodes must be applied to the surface of the human body.
In addition, the transcutaneous measurement of PO.sub.2 and PCO.sub.2 require the attachment of a PO.sub.2 sensitive polarographic sensor and a pH sensitive PCO.sub.2 sensor, respectively, on the surface of the body. FIG. 2 shows a sectional view of typical PO.sub.2 non-invasive sensor assembly.
A rod-shaped cathode 5 is disposed in the center, and an anode 7 is mounted about the cathode 5 with intervening glass insulation 6. The ends of the anode contact an electrolyte 9 which is covered by an electrode membrane 8. The peripheral portion of the electrode 7 is covered by a metal heating ring 10 and a skin-heating metal plate 11. An exposed portion of the skin-heating metal plate 11 is made to contact the skin surface when the sensor assembly is attached to the surface of the body. As described above, four sets of electrodes need be attached to the surface of the human body when the above four functions are to be measured simultaneously. When such a large number of electrodes and sensors are required to be attached to a limited surface area of the patient, it often happens that some of the functions must be measured later due to space limitations. In addition, as the number of electrodes or sensors to be attached increases, the number of electric lead wires will naturally increase and cause difficulties in the handling of the electrodes or sensors in an intensive care unit.